CEPHALOPODA. 103 



No. 218. [519, Cast]. Ammonites modiolaris, Laid. 



Also known as A. siiblcevis, Sow. This is 

 one of the most inflated, yet deeply umbili- 

 cated, of all Ammonite forms. From the 

 Kelloway Rock, Wiltshire, England, and now 

 in the Ward Collection, Universitj- of Roch- 

 ester. 



No. 219. Am.monites Murchisonse, Sow. 



This shell, so characteristic of the inferior Oolite of Europe, probablj^ be- 

 longs to the group " Dentati," the culmination of which is in the Cretaceous 

 series. From Bridport, England. 



No. 220. [523, Cast]. Ammonites peramplus, Mant. 



This gigantic specimen is from the Chalk, Germany. Diameter, 31. 



No. 221. [524, Cast]. Ammonites perarmatus, Sow. 

 From the Oxford Clay (Middle Oolite) Calvados, France. 



Diameter, G. 



No. 222. Ammonites placenta, DeKay. 



This is one of ths most characteristic fossils of our Western Cretaceous. 

 From the Black Hills, Dakota. 



No. 223. Ammonites planicostatus, Sow. 



This small form would appear to belong to the group " Capricmnii," but as 

 it increases in age, it assumes a .single row of spines, in some instances very 

 largely developed, and thus puts on the character of the group "Armati," and 

 becomes the A. Dudressieri, d'Orb. This specimen is a slab covered with 

 numerous shells, and is from the Lower Lias, Dorset. 



